# tikz arrow direction

Can someone help me direct the arrow? \begin{equation}
X \sim Normal({\tikzmark{starta}\mu\tikzmark{enda}}, \sigma^2), \quad com \; f(x) = \frac{1}{\sigma\sqrt{2\pi}}exp\left[\frac{-1}{2}\left(\frac{x - \mu}{\sigma}\right)^2\right]
\end{equation}

\begin{tikzpicture}[remember picture,overlay]
\node [shift={(3.0em,-4.0ex)}, anchor=west] at ({pic cs:starta}) (X) {$\tilde{\mu} = (a, b, c); \textit{\text{média}} \: fuzzy$};
\draw [->,>=latex] (X.west) -| ($({pic cs:starta})!0.5!({pic cs:enda})+(0,-0.5ex)$);
\end{tikzpicture}

• Welcome to TeX.SX! Can you please expand the code snippet that you have posted to a full minimal working example. A MWE should compile and be as small as possible to demonstrate your problem. it's much easier to help you if we have full working code to start from.
– user30471
Sep 24 '17 at 11:48
• This said, it is probably enough to change -> to <-.
– user30471
Sep 24 '17 at 11:48
• -> means put an arrow tip at the end of the line; <- means put an arrow tip on the start of the line; <-> means put arrow tip on both ends of the line. Unrelated: Write \exp, not exp, and use \text for the other things that are text as well (e.g. fuzzy). Sep 24 '17 at 12:00
• any news? so answer below solve your problem? or you simply forgot on your question ... Oct 9 '17 at 23:01

off-topic first:

• please, in question always provide complete small document (called "minimal working example") which start with \documentclass{...} and ending with \end{document} and with necessary packages and definitions in preamble. with it you will help use to help you. it is not fun to complete your code sniped and identify necessary packages from your code. also many times the source of problem lie in preamble.
• what is "Normal"? collection of variables N, o, r, m, a, and o? or math operator? if it is later, than wrote it for example as \mathrm{Normal} or define new math operator
• the same is valid for "com"
• exp is math operator, so it should be writen as \exp
• it seems that "média fuzzy" is text, so it had to be written on such a way.

on topic:

• consider Torbjørn T. comment. as define start and end end of arrow, it should be \draw [latex-] (X.west) -| ($({pic cs:starta})!0.5!({pic cs:enda})+(0,-0.5ex)$);,
• however you can also write as \draw [-latex] ($({pic cs:starta})!0.5!({pic cs:enda})+(0,-0.5ex)$) |- (X.west);

considering aforementioned, the mwe can be as follows:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{calc, tikzmark}

\begin{document}
\begin{equation}
X \sim \mathrm{Normal}({\tikzmark{starta}\mu\tikzmark{enda}}, \sigma^2),
\quad \mathrm{com}\; f(x) = \frac{1}{\sigma\sqrt{2\pi}}\exp\left[\frac{-1}{2}\left(\frac{x - \mu}{\sigma}\right)^2\right]
\end{equation}

\begin{tikzpicture}[remember picture,overlay]
\node (X) [shift={(3em,-5ex)}, anchor=west]
at (pic cs:starta) {$\tilde{\mu} = (a, b, c)$;
média fuzzy};
\draw [-latex] ($({pic cs:starta})!0.5!({pic cs:enda})+(0,-0.5ex)$) |- (X.west);
\end{tikzpicture}
\end{document} 